The Watergate scandal that disgraced Richard Nixon, sullied the presidency, and demoralized a nation was actually a brilliantly-executed conspiracy with one primary goal – to make Sen. Edward Kennedy the next president of the United States. So alleges Geoff Shepard, a former staffer in the Nixon White House and author of the new book, “The Secret Plot to Make Ted Kennedy President.”

There’s just one problem, of course: Kennedy never did become president.

No matter. Shepard tells The Post that virtually every Watergate investigator and prosecutor was a “Kennedy Clan Democrat” who saw a potential Nixon downfall as a chance to regain power; and that “weasel” John Dean masterminded the break-in, then changed his official story to benefit the Kennedy crew.

“The key to the book is that the special prosecutor knew that Dean’s story was changing,” claims Shepard, who attended Nixon’s alma mater, Whittier College, with the benefit of a scholarship partially funded by Nixon himself.

“He was tailoring his story to their needs, and their needs weren’t to prosecute the Watergate crime – that had [already] been solved – it was to use the outrage over Watergate to make Ted Kennedy president.”

Shepard, who served as associate director of the Domestic Council under John Ehrlichman, assisted in Nixon’s legal defense, and performed a final transcription of the infamous Watergate tapes.

He began writing his account of that time in 2002, and while researching Nixon’s papers at the National Archives, realized that the special prosecutor’s papers were there as well.

He requested files on John Dean, Jeb Magruder and G. Gordon Liddy, the three men he calls “the ringleaders of the crime.” Those files led him to his conclusion about the Kennedy Dems.

“These people were robbed of their moment in the sun with the [end of the John F.] Kennedy presidency,” he says. “Teddy was the last surviving brother. If Teddy were president, all these Kennedy Democrats would have a place at the table.”

When ask who masterminded this “plot,” however, Shepard pleads ignorance.

“Don’t know. Can’t tell you that,” he says. “Who is running a school of fish when a school of fish darts in the ocean? Who’s running a flock of birds when they wheel in the sky? You don’t know.”

Shepard’s allegations are also weakened by the basic fact that in the 1976 presidential election, Ted Kennedy didn’t even run. It could be that his personal problems – Chappaquiddick was only six years before – trumped any political advantage.

“We’re not sure why,” he says. “There’s isn’t an announcement. It’s possible his personal life was in turmoil. His marriage was falling apart. It’s possible he didn’t feel he was ready.”

Shepard emphasizes that many of the book’s assertions – including the one made by the title – are merely personal conclusions, not provable facts.

“What I’ve been able to show are certain points of reference,” he says, equating the book to “a game of connect the dots.”

“This is not, ‘I’ve got it, here’s absolute proof, there’s no question,’ ” he says. “It’s ‘here’s a set of facts, a set of memos from inside the special prosecutor’s files that have never been made public.’ That ought to raise concerns about what was done.”

He notes that shortly after the Watergate break-in, Kennedy himself lead an investigation into the Nixon administration before party elders pulled him back, and that special prosecutors were briefed in “secret meetings” by Kennedy’s top counsel about how to conduct the investigation.

And while he believes that Robert Kennedy’s “Get Hoffa” squad – the lawyers RFK, as attorney general, had assigned to help nab the mobster – evolved into a “Get Nixon” squad, he admits to having no evidence that anyone involved with Watergate acted with the intention of electing Ted Kennedy president.

“You see shadows, you get reports, there are certain items of truth, and back to the game of connect the dots,” he says. “In that sense, there is no ‘smoking gun’ memo.”

Hillary Clinton also appears in Shepard’s book, as she was a lawyer for the impeachment inquiry staff of the Judiciary Committee. Shepard claims that Clinton [then Rodham] helped suppress a report on presidential abuses of power, a claim taken not from his own research – he says that her committee’s work is sealed until 2024 – but from an out-of-print book by then-chief counsel for the Judiciary Committee Jerry Zeifman, who two years ago was peddling another book, a self-published paperback titled “Hillary’s Pursuit of Power.”

Shepard reiterates that the book’s main culprit is not Ted Kennedy, but the people who hoped to leverage his power – and, of course, Dean. “John Dean is a weasel,” says Shepard. “He sickens you. They let him go because he was the only path to the people they wanted, and it was the Kennedy Democrats who let him go.”